Microdialysis is a relatively new technique for monitoring the neurochemical processes of the brain and the central nervous system. However, dialysis fibers stereotaxically implanted in the extracellular fluid of the brain react with astrocytes and fibroblasts within one hour. Thus, even short-term experiments to study brain neurophysiology can be affected due to this lack of biocompatibility. In addition, long-term studies are not possible because dialysis fiber pores become occluded and diffusion across the membrane ceases. As a means of improving the biocompatibility of the dialysis fibers in the brain extracellular fluid, dialysis fibers will be surface modified to impart a non-stick, biocompatible surface. Two low temperature plasma techniques, plasma surface modification and plasma polymerization, will be used to alter the surface chemistry of microdialysis membranes. After characterization of the modified surface, in vitro neuron and astrocyte toxicity and amino acid dialysis experiments will be performed.